In this work, the dissolution of iridium was studied through a thermodynamic theoretic study with different concentrations of hydrochloric acid (HCl) and Iridium (Ir). Three different acid conditions and three different concentrations of iridium were analyzed: 1, 0.1 and 0.01 M HCl and 0.86, 0.021 and 0.002 M of iridium. The system 1 M HCl was the only one that presented soluble species of Ir. Results showed that as the Ir concentration diminished from 0.86 to 0.002 M, the pH range where it is possible to obtain Ir soluble species, increased (from 0-1.2 to 0-2). The presence of two Ir species (valences III and IV) for 0.021M and 0.002 M Ir concentrations was determined from the Pourbaix diagrams; while for the 0.086 M concentration, only the Ir (IV) species was observed. The Pourbaix diagrams showed that it is possible to obtain the species iridium (IV) from a potential range of 0.823 V vs SHE to 1.422 V vs SHE and at a pH between 0 and 1.2 in the 1 M HC1 solution.
Cobalt electrodeposition on palladium and glassy carbon was studied at different temperatures by using voltammetric techniques. Temperature effect on the diffusion coefficient value was analyzed. The results clearly showed that cobalt electrodeposition is a diffusioncontrolled process. The temperature effect on the values of the diffusion coefficient was analyzed through the Arrhenius equation. The value of the activation energy was calculated as 21.56 kJ mol-1and 25.73 kJ mol1for palladium and glassy carbon respectively.
In the present work, it was analyzed the palladium electrodeposition onto High Oriented Pyrolitic Graphite (HOPG) electrode from an aqueous solution (0.001 M PdCl2 + 1M NH4Cl (pH 5)) through cyclic voltammetry and chronoamperometry. The analysis of voltammetric data showed that palladium electrodeposition is controlled by mass transfer. From the potentiostatic study it was calculated the diffusion coefficient, the number of active nucleation sites (N0) and the rate constant of the proton reduction process (kPR). It was seen that an increment of N0 and kPR values is obtained when the overpotential applied is increased.
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